Deserializer.java

/*******************************************************************************
 * Copyright (c) 2012-2017 Codenvy, S.A.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.commons.lang;

import java.util.Map;

/** A deserializer that resolve system properties to allow runtime configuration. */
public class Deserializer {
    /**
     * Resolve the variables of type ${my.var} for the current context from the system
     * properties
     *
     * @param input
     *         the input value
     * @return the resolve value
     */
    public static String resolveVariables(String input) {
        return resolveVariables(input, null, true);
    }

    /**
     * Resolve the variables of type ${my.var} for the current context which is composed
     * only of the given settings
     *
     * @param input
     *         the input value
     * @param props
     *         a set of parameters to add for the variable resolution
     * @return the resolve value
     */
    public static String resolveVariables(String input, Map<String, String> props) {
        return resolveVariables(input, props, true);
    }

    /**
     * Resolve the variables of type ${my.var} for the current context which is composed
     * of the system properties and the given settings
     *
     * @param input
     *         the input value
     * @param props
     *         a set of parameters to add for the variable resolution
     * @return the resolve value
     */
    public static String resolveVariables(String input, Map<String, String> props, boolean includeSysProps) {
        final int NORMAL = 0;
        final int SEEN_DOLLAR = 1;
        final int IN_BRACKET = 2;
        if (input == null) {
            return input;
        }
        if (!includeSysProps && (props == null || props.size() == 0)) {
            return input;
        }
        char[] chars = input.toCharArray();
        StringBuffer buffer = new StringBuffer();
        boolean properties = false;
        int state = NORMAL;
        int start = 0;
        for (int i = 0; i < chars.length; ++i) {
            char c = chars[i];
            if (c == '$' && state != IN_BRACKET) {
                state = SEEN_DOLLAR;
            } else if (c == '{' && state == SEEN_DOLLAR) {
                buffer.append(input.substring(start, i - 1));
                state = IN_BRACKET;
                start = i - 1;
            } else if (state == SEEN_DOLLAR) {
                state = NORMAL;
            } else if (c == '}' && state == IN_BRACKET) {
                if (start + 2 == i) {
                    buffer.append("${}");
                } else {
                    String value = null;
                    String key = input.substring(start + 2, i);

                    if (props != null) {
                        // Some parameters have been given thus we need to check
                        // inside first
                        String sValue = props.get(key);
                        value = sValue == null || sValue.length() == 0 ? null : sValue;
                    }
                    if (value == null && includeSysProps) {
                        // try to get it from the system properties
                        value = System.getProperty(key);
                    }

                    if (value != null) {
                        properties = true;
                        buffer.append(value);
                    }
                }
                start = i + 1;
                state = NORMAL;
            }
        }
        if (properties == false) {
            return input;
        }
        if (start != chars.length) {
            buffer.append(input.substring(start, chars.length));
        }
        return buffer.toString();
    }
}